Investments - Summary of Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Total	$ 503,040	$ 703,267
Gross Unrealized Gains	6,898	2,031
Gross Unrealized Losses	(80)	(343)
Estimated Fair Value	509,858	704,955
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Total	3,899	5,118
Gross Unrealized Gains	98	27
Gross Unrealized Losses	0	0
Estimated Fair Value	3,997	5,145
Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Total	366,484	471,172
Gross Unrealized Gains	6,386	1,950
Gross Unrealized Losses	(74)	(214)
Estimated Fair Value	372,796	472,908
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Total	21,040	48,086
Gross Unrealized Gains	77	2
Gross Unrealized Losses	(1)	(19)
Estimated Fair Value	21,116	48,069
U.S. Government agencies
Debt Securities, Available-for-sale [Line Items]
Total	111,617	178,891
Gross Unrealized Gains	337	52
Gross Unrealized Losses	(5)	(110)
Estimated Fair Value	$ 111,949	$ 178,833

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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